No VAT to pay — but nothing to reclaim either.
Then no margin VAT is due for that period, and you get nothing back: a negative margin does not create a credit. The shortfall may usually be carried forward to the next period, where it lowers your margin there. Discuss the carry-over with your accountant — for the Netherlands the Belastingdienst puts it in exactly those words.
This happens more often than you would think in a shop with expensive pieces: buy a lot in March and sell it only in June, and the first quarter is negative while the second is high.
So it is not a bookkeeping error but a consequence of your buying rhythm. What does go wrong is a shortfall you forget to carry over: you then pay, in the next period, on a margin that was really lower.
Sources, each checked on 31 August 2026: Royal Decree no. 53 of 23 December 1994 (Belgium), Belastingdienst (Netherlands), article 297 A-II of the CGI and BOI-TVA-SECT-90-20 on bofip.impots.gouv.fr (France), and gov.uk (UK).
This is an explanation, not tax or legal advice. Put your own situation to your accountant.
In Belgium the profit margin is looked at per return period: you add up all purchases and all sales in the period and only then take the difference. That is the globalisation method. In France the statutory default is per piece, with globalisation as an option; in the UK the Margin Scheme is per piece and Global Accounting per period.
Add up what you paid for the pieces still standing. Not your asking prices: those are an expectation, not a value. You need that figure for your year-end accounts, and it is also the denominator of your stock turnover.
Vintro Pro keeps, per piece, what you paid, when, and where it came from. Your stock list and your margin VAT build themselves while you work.
Free up to 10 pieces, no card number and no end date.